Studies on the mechanism of implant‐induced supernumerary limb formation in urodeles. I. The histology of supernumerary limb formation in the adult newt, triturus viridescens

Abstract

Supernumerary structures were formed in adult Triturus forelimbs following subcutaneous implantation of pieces of frog kidney. The gross and microscopic events in supernumerary limb formation were described in this paper. The first few days after implantation comprise a stage of wound healing and phagocytosis, the latter by both the epidermis and inflammatory cells of the host. Following this the tubular portions of the implant degenerate. During the height of this degeneration, the first dedifferentiated cells of the host are seen. These cells increase in number and gather around a central focus to form a blastema. From the blastema, first cartilage and then muscle differentiate, and elongation proceeds concomitantly with this differentiation. The final result of the kidney implant may be no growth at all, periosteal chondrification not preceded by a blastema or a true supernumerary structure ranging in complexity from a cartilaginous nodule to a fully developed supernumerary limb. The results of this experiment indicate that aside from the initial stimulus and the ultimate degree of morphogenetic complexity attained, the development of a supernumerary structure is very similar to the regeneration of an amputated limb.

The Distribution of Supernumerary Limb-inducing Capacity in Tissues of <i>Rana pipiens</i>

“…He also demonstrated that implants of normal adult frog kidney induced supernumerary limbs in adult newts in close to 100% of cases [16]. Carlson [3] confirmed these findings and re ported on the ontogénie development of the supernumerary limb-inducing capacity in frog kidney as well as the ability of certain other tissues to induce accessory limbs [4]. Ruben et al [17,20] have reported on the capacity for supernumerary limb induction of several other types of frog tissues.…”

“…The host newts were anesthetized in 1:1000 MS 222, and 1 mm3 pieces of frog tissues were implanted singly under the skin of the upper arms according to a technique pre viously described [3]. Following the operations, the newts were placed in groups of 5 in large glass culture dishes and maintained for 60 days at a temperature of 2I°C.…”

The Effect of X-irradiation and Beryllium Nitrate upon Implant-induced Supernumerary Limb Formation in the Newt

“…The close resemblance between the histological events occurring during the formation of a supernumerary limb and those in post-amputational regeneration was demonstrated by C a r l s o n [8]. Corresponding with this viewpoint are the results of Peredelsky [15] who found that in R a n a te m p o ra ria the ability to regenerate a limb and the ability to form implant-induced accessory structures were lost at the same stage of metamorphosis.…”

“…The basic implantation operation was the same as that described previously [8,9], but in the animals included in the irradiation experiments one exception is to be noted. For greater assurance that the implants would be placed in completely irradiated areas, the forearms were used as implantation sites.…”

The ability of localized implants of whole or minced dermis to disrupt pattern formation in the regenerating forelimb of the axolotl

“…intestine (Nassonov, 1938b;Carlson, 1971), and gills (Nassonov, 1938c) causes supernumerary limbs to form at the site of implantation in newts and axolotls. The kidney and urinary system of both frogs and salamanders have been shown to be particularly influential in this process (Ruben, 1957(Ruben, , 1960bRuben and Frothingham, 1958;Bodemer, 1959;Stevens, 1962, 1963a.b;Stevens et al, 1965;Carlson, 1967Carlson, , 1968Carlson, , 1970Carlson, , 1971Carlson, , 1974a. These studies have served to demonstrate the ability of non-limb tissues to stimulate a regenerative response in an unamputated limb.…”